Magnetic ferrites have been produced using iron oxide, zinc oxide, nickel oxide, manganese oxide and magnesium oxide as the main components. Namely, Mn—Zn ferrite, Ni—Zn ferrite and Mg ferrite are the basic compositions of ferrites, or the spinel type ferrites. Proportion among the main components and amount of side components added as additive are varied depending on the field of application. Magnetic ferrites have been manufactured in the above-described manner, and used widely in quite a number of electronic circuits operating in the low frequency zone up to the high frequency of approximately 200 MHz.
Magnetic devices used in the electronic circuits are made to demonstrate varieties of characteristics by taking advantage of the following basic functioning rule of the core ferrite:
Complex permeability μ=μ′−μ″×i (μ′: permeability, μ″: loss factor).
Recently, for use in the frequency zone higher than 200 MHz, a hexagonal crystal ferrite containing iron oxide, barium oxide and strontium oxide as the main components was introduced.
Japanese Patent Unexamined Publication No. H5-36517 discloses an example of the magnetic material containing the hexagonal crystal ferrite.
The above-described conventional magnetic ferrites, however, exhibit the sudden increase of loss factor μ″ at a frequency lower than 1 GHz. This means that the magnetic devices containing conventional magnetic ferrites can be used only in a frequency zone lower than 1 GHz. On the other hand, the high frequency technology is making a remarkable progress in the sector of digital electronic appliances which requires magnetic devices for great numbers.
In order to meet the emerging needs for processing broad band signals at high speed, the circuit components are requested to be capable of handling the signals of still higher frequency.
The present invention addresses the above problem and aims to offer a magnetic ferrite in which the sudden rise of loss factor μ″ occurs only in a frequency zone higher than 1 GHz. The present invention also aims to realize, by making use of the magnetic ferrite, a magnetic device that can be used in the frequency zone higher than 1 GHz.